Jimmy Fallon sings "Fancy" as Neil Young along with Crosby, Stills and Nash

Jimmy Fallon was up to his fun tricks again when he stepped on stage disguised as Neil Young singing Iggy Azalea's hit "Fancy" with "his" former band members David Crosby, Stephen Stills and Graham Nash.

During the Tonight Show Monday night, Fallon helped the former band reunite by impersonating Neil Young and doing a performance together just like in the olden days. Except, this time, the tune was actually a popular, current rap song.

Wearing Young's typical stage gear — consisting of a wide-brimmed hat, camel-colored jacket, plaid shirt and old jeans — Fallon sang along and also took time for a solo on his neck-harnessed harmonica. A minute or so into it, the rest of the band appeared and began singing backup as the audience exploded into cheer.

"I'm so fancy, you already know / I'm in the fast lane / from LA to Tokyo," Fallon and the group sang without missing a beat.

Managing to stay straight-faced and serious, the group performed the song flawlessly, and other than the song's lyrics, it was impossible to tell that they were singing a contemporary hit. The music style was so spot on — it actually sounded as if Young and his former Crosby, Stills & Nash band were on stage singing away like old times.